Reduced Activation of RAF-1 and MAP Kinase by a Fibroblast Growth Factor Receptor Mutant Deficient in Stimulation of Phosphatidylinositol Hydrolysis (*)
- From the (1)Department of Pharmacology, New York University Medical Center, New York, New York 10016
- **To whom correspondence should be addressed: Dept. of Pharmacology, New York University Medical Center, 550 First Ave., New York, NY. Tel.: 212-263-7111; Fax: 212-263-7133.
Abstract
Signaling via the fibroblast growth factor receptor 1 (FGFR1, flg) was analyzed in Ba/F3 hematopoietic cells expressing either wild-type or a mutant FGF receptor (Y766F) unable to activate
phospholipase C-
(PLC-
) and stimulate phosphatidylinositol (PI) hydrolysis. Stimulation of cells expressing wild-type or mutant FGFR with acidic
FGF (aFGF) caused similar activation of Ras. However, an approximately 3-fold reduced activation of Raf-1 and MAP kinase was
observed in aFGF-stimulated cells expressing mutant receptors as compared to cells expressing wild-type FGF receptors. Comparison
of phosphopeptide maps of Raf-1 immunoprecipitated from the two cell types activated by either aFGF or the phorbol ester (12-O-tetradecanoylphorbol-13-acetate) suggests that Raf-1 is phosphorylated by both Ras-dependent and PLC-
-dependent mechanisms. In spite of the differential effect on Raf-1 and MAP kinase activation, aFGF stimulated similar proliferation
of cells expressing wild-type or mutant receptors indicating that Ras-dependent activation of Raf-1 and MAP kinase is sufficient
for transduction of FGFR mitogenic signals. Ras may also activate signal transduction pathways that are complementary or parallel
to the MAP kinase pathway to stimulate cell proliferation.
Footnotes
-
↵§ Fellow of the Leukemia Society of America.
-
↵¶ Supported by a long term fellowship from the International Human Frontier Science Program Organization (HFSPO).
-
↵* This work was supported in part by a grant from Sugen (to J. S.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
1 The abbreviations used are:
- GAP
-
GTPase-activating protein
- FGF
-
fibroblast growth factor
- FGFR
-
FGF receptor
- aFGF
-
acidic FGF
- PLC
-
phospholipase C
- PI
-
phosphatidylinositol
- MAP
-
microtubule-associated protein
- TPA
-
12-O-tetradecanoylphorbol-13-acetate
- MAPK
-
MAP kinase
- PDGF
-
platelet-derived growth factor
- NGF
-
nerve growth factor
- EGF
-
epidermal growth factor
- IL
-
interleukin
- PKC
-
protein kinase C
- PAGE
-
polyacrylamide gel electrophoresis.
-
2K. Degenhardt, N. Li, N. W. Gale, M. Mohammadi, J. Schlessinger, and D. Bar-Sagi, manuscript submitted for publication.
-
- Received October 7, 1994.
- Revision received December 5, 1994.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
